U.S. patent application number 15/489752 was filed with the patent office on 2017-11-16 for electrostatic scanner having sensing comb assemblies.
This patent application is currently assigned to Ultimems, Inc.. The applicant listed for this patent is Ultimems, Inc.. Invention is credited to Yee-Chung Fu, Han-Tang Su.
Application Number | 20170328942 15/489752 |
Document ID | / |
Family ID | 60294603 |
Filed Date | 2017-11-16 |
United States Patent
Application |
20170328942 |
Kind Code |
A1 |
Fu; Yee-Chung ; et
al. |
November 16, 2017 |
ELECTROSTATIC SCANNER HAVING SENSING COMB ASSEMBLIES
Abstract
An electrostatic scanner is disclosed. The electrostatic scanner
comprises a mirror, one or more actuating comb assemblies, one or
more sensing comb assemblies and two or more springs. The one or
more sensing comb assemblies each have a movable sensing combteeth
set, an upper fixed sensing combteeth set and a lower fixed sensing
combteeth set. The upper fixed sensing combteeth set and the
movable sensing combteeth set form an in-plane comb configuration.
The lower fixed sensing combteeth set and the movable sensing
combteeth set form a vertical comb configuration. An upper fixed
sensing combtooth of the upper fixed sensing combteeth set is
shorter than a lower fixed sensing combtooth of the lower fixed
sensing combteeth set.
Inventors: |
Fu; Yee-Chung; (Fremont,
CA) ; Su; Han-Tang; (Taichung City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ultimems, Inc. |
New Taipei City |
|
TW |
|
|
Assignee: |
Ultimems, Inc.
New Taipei City
TW
|
Family ID: |
60294603 |
Appl. No.: |
15/489752 |
Filed: |
April 18, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62333846 |
May 10, 2016 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 26/0841 20130101;
G01R 29/12 20130101 |
International
Class: |
G01R 29/12 20060101
G01R029/12 |
Claims
1. An electrostatic scanner comprising: a mirror to rotate about a
first direction; one or more vertically actuating comb assemblies
including: a first vertically actuating comb assembly containing: a
first movable actuating combteeth set to rotate about the first
direction; and a first fixed actuating combteeth set extending
along a second direction perpendicular to the first direction; and
one or more sensing comb assemblies including: a first sensing comb
assembly containing: a first movable sensing combteeth set to
rotate about the first direction; a first upper fixed sensing
combteeth set extending along the second direction; and a first
lower fixed sensing combteeth set extending along the second
direction; wherein combteeth of the first upper fixed sensing
combteeth set are shorter than combteeth of the first lower fixed
sensing combteeth set; wherein the first upper fixed sensing
combteeth set and the first movable sensing combteeth set form an
in-plane comb configuration; and wherein the first lower fixed
sensing combteeth set and the first movable sensing combteeth set
form a vertical comb configuration.
2. The electrostatic scanner of claim 1, wherein the first upper
fixed sensing combteeth set is electrically connected to a first
upper pad; wherein the first lower fixed sensing combteeth set is
electrically connected to a first lower pad; and wherein a wire
mechanically and electrically connects the first upper pad to the
first lower pad.
3. The electrostatic scanner of claim 1, wherein the first upper
fixed sensing combteeth set is electrically connected to a first
upper pad; wherein the first lower fixed sensing combteeth set is
electrically connected to a first lower pad; wherein a connecting
pad mechanically and electrically connects the first upper pad to
the first lower pad; and wherein the connecting pad is attached to
a vertical wall between the first upper pad and the first lower
pad.
4. The electrostatic scanner of claim 1, wherein the first upper
fixed sensing combteeth set is electrically connected to a first
upper electrode; wherein the first lower fixed sensing combteeth
set is electrically connected to a first lower electrode; and
through silicon vias mechanically and electrically connect the
first upper electrode to the first lower electrode.
5. The electrostatic scanner of claim 1, wherein the first upper
fixed sensing combteeth set is electrically connected to a first
upper electrode; wherein the first lower fixed sensing combteeth
set is electrically connected to a first lower electrode; and the
first upper electrode and the first lower electrode are
eutectically bonded.
6. The electrostatic scanner of claim 1 further comprising an
insulation layer between the first upper fixed sensing combteeth
set and the first lower fixed sensing combteeth set; wherein the
first upper fixed sensing combteeth set is directly attached to a
top surface of the insulation layer; and wherein the first lower
fixed sensing combteeth set is directly attached to a bottom
surface of the insulation layer.
7. The electrostatic scanner of claim 1 further comprising a base
made of a glass material.
8. The electrostatic scanner of claim 1 further comprising a frame,
wherein the first movable actuating combteeth set and the first
movable sensing combteeth set extend away from the frame.
9. The electrostatic scanner of claim 8, wherein combteeth of the
first movable actuating combteeth set and combteeth of the first
movable sensing combteeth set have a same length.
10. The electrostatic scanner of claim 1, wherein a first gap in
the first direction between a combtooth of the first movable
sensing combteeth set and an adjacent upper combtooth of the first
upper fixed sensing combteeth set is larger than a second gap in
the first direction between the combtooth of the first movable
sensing combteeth set and an adjacent lower combtooth of the first
lower fixed sensing combteeth set.
11. The electrostatic scanner of claim 1, wherein combteeth of the
first movable actuating combteeth set and the first fixed actuating
combteeth set are of tapered shapes.
12. The electrostatic scanner of claim 1, wherein combteeth of the
first movable sensing combteeth set, the first upper fixed sensing
combteeth set and the first lower fixed sensing combteeth set are
of tapered shapes.
13. The electrostatic scanner of claim 1, wherein the one or more
vertically actuating comb assemblies are symmetric with respect to
the first direction and are symmetric with respect to the second
direction.
14. The electrostatic scanner of claim 1, wherein the one or more
sensing comb assemblies are asymmetric with respect to the first
direction and are symmetric with respect to the second
direction.
15. The electrostatic scanner of claim 1 further comprising a first
and second springs to rotate about the first direction, wherein the
first and second springs are symmetric with respect to the second
direction.
16. The electrostatic scanner of claim 15 further comprising a
third and fourth springs to rotate about the first direction,
wherein the third spring is between the mirror and the first
spring; and wherein the fourth spring is between the mirror and the
second spring.
17. The electrostatic scanner of claim 15 further comprising a
third and fourth springs to rotate about the second direction,
wherein the third and fourth springs are symmetric with respect to
the first direction.
18. An electrostatic scanner comprising: a mirror to rotate about a
first direction; one or more vertically actuating comb assemblies
including: a first vertically actuating comb assembly containing: a
first movable actuating combteeth set to rotate about the first
direction; and a first fixed actuating combteeth set extending
along a second direction perpendicular to the first direction; and
one or more sensing comb assemblies including: a first sensing comb
assembly containing: a first movable sensing combteeth set to
rotate about the first direction; a first upper fixed sensing
combteeth set extending along the second direction; and a first
lower fixed sensing combteeth set extending along the second
direction; wherein the first upper fixed sensing combteeth set and
the first movable sensing combteeth set form an in-plane comb
configuration; wherein the first lower fixed sensing combteeth set
and the first movable sensing combteeth set form a vertical comb
configuration; and wherein a first gap in the first direction
between a combtooth of the first movable sensing combteeth set and
an adjacent upper combtooth of the first upper fixed sensing
combteeth set is larger than a second gap in the first direction
between the combtooth of the first movable sensing combteeth set
and an adjacent lower combtooth of the first lower fixed sensing
combteeth set.
19. An electrostatic scanner comprising: a mirror to rotate about a
first direction; one or more vertically actuating comb assemblies
including: a first vertically actuating comb assembly containing: a
first movable actuating combteeth set to rotate about the first
direction; and a first fixed actuating combteeth set extending
along a second direction perpendicular to the first direction; and
one or more sensing comb assemblies including: a first sensing comb
assembly containing: a first movable sensing combteeth set to
rotate about the first direction; a first upper fixed sensing
combteeth set extending along the second direction; and a first
lower fixed sensing combteeth set extending along the second
direction; wherein the first upper fixed sensing combteeth set and
the first movable sensing combteeth set form a vertical comb
configuration; and wherein the first lower fixed sensing combteeth
set and the first movable sensing combteeth set form an in-plane
comb configuration.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application claims benefit of a provisional
patent application 62/333,846. The disclosure made in the
provisional patent application 62/333,846 is hereby incorporated by
reference. U.S. Pat. No. 7,014,115 to Fu, U.S. Pat. No. 7,538,927
to Fu and U.S. Pat. No. 9,201,239 to Fu are hereby incorporated by
reference.
FIELD OF THE INVENTION
[0002] This invention relates generally to an electrostatic
scanner. More particularly, the present invention relates to a
Micro-Electro Mechanical Systems (MEMS) electrostatic scanner
having sensing comb assemblies.
BACKGROUND OF THE INVENTION
[0003] U.S. Pat. No. 7,014,115 to Fu discloses a MEMS scanning
mirror with distributed hinges and multiple support attachments.
FIG. 1A, 1B, 1C, 2, 3, and 4 of U.S. Pat. No. 7,538,927 to Fu
discloses a process to construct a scanning mirror with short
vertical combteeth in a vertical comb drive and long in-plane
combteeth in an in-plane comb drive. U.S. Pat. No. 9,201,239 to Fu
discloses a two-dimensional electrostatic scanner with distributed
springs. This invention discloses an electrostatic scanner having
sensing comb assemblies. One of the advantages of the present
invention is that angular positions of the mirror can be determined
by measuring the capacitance from the sensing comb assemblies. The
determined angular positions of the mirror can be used for feedback
control.
SUMMARY OF THE INVENTION
[0004] This invention discloses an electrostatic scanner comprising
a mirror, one or more actuating comb assemblies, one or more
sensing comb assemblies and two or more springs. The one or more
sensing comb assemblies each have a movable sensing combteeth set,
an upper fixed sensing combteeth set and a lower fixed sensing
combteeth set. The upper fixed sensing combteeth set and the
movable sensing combteeth set form an in-plane comb configuration.
The lower fixed sensing combteeth set and the movable sensing
combteeth set form a vertical comb configuration. An upper fixed
sensing combtooth of the upper fixed sensing combteeth set is
shorter than a lower fixed sensing combtooth of the lower fixed
sensing combteeth set.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a schematic perspective view of an electrostatic
scanner in examples of the present disclosure.
[0006] FIG. 2 is a top view of an upper layer of the electrostatic
scanner of FIG. 1 in examples of the present disclosure.
[0007] FIG. 3 is a top view of a lower layer of the electrostatic
scanner of FIG. 1 in examples of the present disclosure.
[0008] FIG. 4 is a top view of a portion of a sensing comb assembly
of the electrostatic scanner of FIG. 1 in examples of the present
disclosure.
[0009] FIG. 5 shows a capacitance versus angle curve of a sensing
comb assembly in examples of the present disclosure.
[0010] FIG. 6 shows a derivative of capacitance with respect to
angle versus angle curve of a sensing comb assembly in examples of
the present disclosure.
[0011] FIG. 7 is a schematic perspective view of an electrostatic
scanner in examples of the present disclosure.
[0012] FIG. 8 is a schematic perspective view of a two-dimensional
electrostatic scanner in examples of the present disclosure.
[0013] FIG. 9 is a schematic perspective view of an electrostatic
scanner in examples of the present disclosure.
[0014] FIG. 10 is a cross-sectional view of through silicon
vias.
[0015] FIG. 11 is a cross-sectional view of through silicon
vias.
[0016] FIG. 12 is a cross-sectional view of eutectic bonded
electrodes.
[0017] FIG. 13 is a schematic perspective view of an electrostatic
scanner in examples of the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0018] FIG. 1 is a schematic perspective view of an electrostatic
scanner 100 in examples of the present disclosure. The
electrostatic scanner 100 comprises an upper layer 102, a lower
layer 104, and a base 106. The upper layer 102 is higher than the
lower layer 104. The lower layer 104 is higher than the base 106.
In examples of the present disclosure, the upper layer 102 and the
lower layer 104 is separated by an insulation layer 108. The
electrostatic scanner 100 includes a mirror 110, four vertically
actuating comb assemblies 112, 114, 116 and 118, two sensing comb
assemblies 122 and 124, a frame 160, and two springs 162 and 164.
The mirror rotates about X-axis. Combteeth of the four vertically
actuating comb assemblies 112, 114, 116 and 118 and combteeth of
the two sensing comb assemblies 122 and 124 extend parallel to
Y-axis.
[0019] The two springs 162 and 164 rotate about the X-axis. The two
springs 162 and 164 are symmetric with respect to the Y-axis.
[0020] In examples of the present disclosure, the four vertically
actuating comb assemblies 112, 114, 116 and 118 are symmetric with
respect to the X-axis and are symmetric with respect to the Y-axis.
In examples of the present disclosure, the two sensing comb
assemblies 122 and 124 are asymmetric with respect to the X-axis
and are symmetric with respect to the Y-axis. To reduce the added
inertia of the moving part of the electrostatic scanner 100, no
sensing comb assemblies are located at Y>0.
[0021] In examples of the present disclosure, the electrostatic
scanner 100 further includes a plurality of upper pads (for
example, upper pad 192) and a plurality of lower pads (for example,
lower pad 194). In examples of the present disclosure, a wire 182
mechanically connects the upper pad 192 to the lower pad 194.
[0022] In examples of the present disclosure, the upper layer 102
and the lower layer 104 are made of a silicon material. The base
106 is made of a glass material. The insulation layer 108 is made
of a silicon dioxide material.
[0023] FIG. 2 is a top view of the upper layer 102 of the
electrostatic scanner 100 of FIG. 1 in examples of the present
disclosure. FIG. 3 is a top view of the lower layer 104 of the
electrostatic scanner 100 of FIG. 1 in examples of the present
disclosure. The vertically actuating comb assembly 112 of FIG. 1
comprises a movable actuating combteeth set 112M of FIG. 2 and a
fixed actuating combteeth set 112F of FIG. 3. The movable actuating
combteeth set 112M rotates about the X-axis. Viewing along Z-axis,
the movable actuating combteeth set 112M and the fixed actuating
combteeth set 112F are interdigitated.
[0024] The sensing comb assembly 122 of FIG. 1 comprises a movable
sensing combteeth set 132 of FIG. 2, an upper fixed sensing
combteeth set 142 of FIG. 2 and a lower fixed sensing combteeth set
152 of FIG. 3. In examples of the present disclosure, the upper
fixed sensing combteeth set 142 and the movable sensing combteeth
set 132 are made from the upper layer 102. Therefore, the upper
fixed sensing combteeth set 142 and the movable sensing combteeth
set 132 form an in-plane comb configuration. In examples of the
present disclosure, the movable sensing combteeth set 132 is made
from the upper layer 102 and the lower fixed sensing combteeth set
152 is made from the lower layer 104. Therefore, the lower fixed
sensing combteeth set 152 and the movable sensing combteeth set 132
form a vertical comb configuration. The movable sensing combteeth
set 132 rotates about the X-axis. The movable sensing combteeth set
132 and the upper fixed sensing combteeth set 142 are
interdigitated. Viewing along Z-axis, the movable sensing combteeth
set 132 and the lower fixed sensing combteeth set 152 are
interdigitated.
[0025] In examples of the present disclosure, the upper fixed
sensing combteeth set 142 is electrically connected to the upper
pad 192 of FIG. 1 and the lower fixed sensing combteeth set 152 is
electrically connected to the lower pad 194 of FIG. 1.
[0026] In examples of the present disclosure, the movable actuating
combteeth set 112M and the movable sensing combteeth set 132 extend
away from the frame 160 of FIG. 1. In examples of the present
disclosure, combteeth of the movable actuating combteeth set 112M
and combteeth of the movable sensing combteeth set 132 have a same
length. In examples of the present disclosure, combteeth of the
movable actuating combteeth set 112M, combteeth of the fixed
actuating combteeth set 112F, combteeth of the movable sensing
combteeth set 132, combteeth of the upper fixed sensing combteeth
set 142 and combteeth of the lower fixed sensing combteeth set 152
are of tapered shapes.
[0027] FIG. 4 is a top view of a movable sensing combtooth 132A of
the movable sensing combteeth set 132 of FIG. 2, an upper fixed
sensing combtooth 142A of the upper fixed sensing combteeth set 142
of FIG. 2 and a lower fixed sensing combtooth 152A of the lower
fixed sensing combteeth set 152 of FIG. 3. During an electrostatic
scanner resting state, the movable sensing combtooth 132A is at a
same height as the upper fixed sensing combtooth 142A. During an
electrostatic scanner resting state, the movable sensing combtooth
132A is located at a position higher than the lower fixed sensing
combtooth 152A.
[0028] In examples of the present disclosure, the upper fixed
sensing combtooth 142A is shorter than the lower fixed sensing
combtooth 152A. A gap 420 in the X-direction between the movable
sensing combtooth 132A and the upper fixed sensing combtooth 142A
is larger than a gap 440 in the X-direction between the movable
sensing combtooth 132A and the lower fixed sensing combtooth
152A.
[0029] FIG. 5 shows a capacitance versus angle curve 502 of a
sensing comb assembly in examples of the present disclosure. From
-8 degrees to 7 degrees, the curve 502 has a substantially constant
slope. The angular position of the mirror 110 can be determined by
the measured capacitance.
[0030] FIG. 6 shows a derivative of capacitance with respect to
angle versus angle curve 602 of a sensing comb assembly in examples
of the present disclosure. Zero-degree angle corresponds to a
resting state of the electrostatic scanner. A positive angle
corresponds to engaging of the movable sensing combteeth set 132 of
FIG. 2 and the lower fixed sensing combteeth set 152 of FIG. 3. A
negative angle corresponds to a condition that a top surface of the
movable sensing combteeth set 132 of FIG. 2 is at a position higher
than a top surface of the upper fixed sensing combteeth set 142 of
FIG. 2. Curve 602 has a substantially flat portion 604 and a sloped
portion 606. Portion 604 corresponds to an in-plane comb
configuration. Portion 606 corresponds to a vertical comb
configuration with minor contribution from the in-plane comb
configuration.
[0031] FIG. 7 is a schematic perspective view of an electrostatic
scanner 700 in examples of the present disclosure. The
electrostatic scanner 700 comprises an upper layer 702, a lower
layer 704, and a base 706. In examples of the present disclosure,
the upper layer 702 and the lower layer 704 is separated by an
insulation layer 708. The electrostatic scanner 700 includes a
mirror 110, four vertically actuating comb assemblies 112, 114, 116
and 118, two sensing comb assemblies 122 and 124, and four springs
162, 164, 766 and 768. The mirror rotates about X-axis. Combteeth
of the four vertically actuating comb assemblies 112, 114, 116 and
118 and combteeth of the two sensing comb assemblies 122 and 124
extend parallel to Y-axis.
[0032] In examples of the present disclosure, the electrostatic
scanner 700 further includes a plurality of upper pads (for
example, upper pad 192) and a plurality of lower pads (for example,
lower pad 194). In examples of the present disclosure, a wire 182
mechanically and electrically connects the upper pad 192 to the
lower pad 194.
[0033] The four springs 162, 164, 766 and 768 rotate about the
X-axis. The four springs 162, 164, 766 and 768 are symmetric with
respect to the Y-axis. The spring 766 is between the mirror 110 and
the spring 162. The spring 768 is between the mirror 110 and the
spring 164.
[0034] FIG. 8 is a schematic perspective view of an electrostatic
scanner 800 in examples of the present disclosure. The
electrostatic scanner 800 comprises an upper layer 802, a lower
layer 804, and a base 806. In examples of the present disclosure,
the upper layer 802 and the lower layer 804 is separated by an
insulation layer 808. The electrostatic scanner 800 includes a
mirror 110, four vertically actuating comb assemblies 112, 114, 116
and 118, two sensing comb assemblies 122 and 124, one or more
in-plane actuating comb assemblies 812, two or more X-directional
springs 162 and 164, and two Y-directional springs 866 and 868. The
mirror rotates about X-axis. Combteeth of the four vertically
actuating comb assemblies 112, 114, 116 and 118 and combteeth of
the two sensing comb assemblies 122 and 124 extend parallel to
Y-axis.
[0035] In examples of the present disclosure, the electrostatic
scanner 800 further includes a plurality of upper pads (for
example, upper pad 192) and a plurality of lower pads (for example,
lower pad 194). In examples of the present disclosure, a wire 182
mechanically connects the upper pad 192 to the lower pad 194.
[0036] The two Y-directional springs 866 and 868 rotate about the
Y-axis. The two Y-directional springs 866 and 868 are symmetric
with respect to the X-axis.
[0037] FIG. 9 is a schematic perspective view of an electrostatic
scanner 900 in examples of the present disclosure. The
electrostatic scanner 900 comprises an upper layer 902, a lower
layer 904, and a base 906. The electrostatic scanner 900 includes a
mirror 110, four vertically actuating comb assemblies 112, 114, 116
and 118, two sensing comb assemblies 122 and 124, and two springs
162 and 164. The mirror rotates about X-axis. Combteeth of the four
vertically actuating comb assemblies 112, 114, 116 and 118 and
combteeth of the two sensing comb assemblies 122 and 124 extend
parallel to Y-axis.
[0038] FIGS. 10-12 are examples of cross-sections along AA of FIG.
9. In examples of the present disclosure, the electrostatic scanner
900 further includes a region 944 having through silicon vias or
having eutectic bonded electrodes. In one example, the upper fixed
sensing combteeth set 142 of FIG. 2 and the lower fixed sensing
combteeth set 152 of FIG. 3 are electrically and mechanically
connected by through silicon via 1020 of FIG. 10 or through silicon
via 1140 of FIG. 11. The through silicon via 1020 of FIG. 10 is
between horizontal insulation 1022 and vertical insulation 1024.
The through silicon via 1140 of FIG. 11 is between horizontal
insulation 1142. In another example, the upper fixed sensing
combteeth set 142 of FIG. 2 is connected to an upper electrode. The
lower fixed sensing combteeth set 152 of FIG. 3 is connected to a
lower electrode. The upper and lower electrodes are eutectically
bonded to form eutectic bonded electrodes 1260 of FIG. 12. The
eutectic bonded electrodes 1260 of FIG. 12 are between horizontal
insulation 1262.
[0039] FIG. 13 is a schematic perspective view of an electrostatic
scanner 1300 in examples of the present disclosure. The
electrostatic scanner 1300 comprises an upper layer 1302, a lower
layer 1304, and a base 1306. The electrostatic scanner 1300
includes a mirror 1310, four vertically actuating comb assemblies
1312, 1314, 1316 and 1318, two sensing comb assemblies 1322 and
1324, and two springs 1362 and 1364. The mirror rotates about
X-axis. Combteeth of the four vertically actuating comb assemblies
1312, 1314, 1316 and 1318 and combteeth of the two sensing comb
assemblies 1322 and 1324 extend parallel to Y-axis.
[0040] The electrostatic scanner 1300 is similar to the
electrostatic scanner 100 of FIG. 1 except that movable parts of
the electrostatic scanner 1300 are in the lower layer 1304. The
lower layer 1304 includes the mirror 1310, a movable actuating
combteeth set of the vertically actuating comb assembly 1312, a
movable sensing combteeth set of the sensing comb assembly 1322,
and a lower fixed sensing combteeth set of the sensing comb
assembly 1322. The upper layer 1302 includes an upper fixed sensing
combteeth set of the sensing comb assembly 1322. The upper fixed
sensing combteeth set of the sensing comb assembly 1322 and the
movable sensing combteeth set of the sensing comb assembly 1322
form a vertical comb configuration. The lower fixed sensing
combteeth set of the sensing comb assembly 1322 and the movable
sensing combteeth set of the sensing comb assembly 1322 form an
in-plane comb configuration.
[0041] In examples of the present disclosure, the electrostatic
scanner 1300 further includes a plurality of upper pads (for
example, upper pad 1392) and a plurality of lower pads (for
example, lower pad 1394). A connecting pad 1398 mechanically
connects the upper pad 1392 to the lower pad 1394. The connecting
pad 1398 is directly attached to the vertical wall between the
upper pad 1392 and the lower pad 1394. In one example, the
connecting pad 1398 is deposited onto the vertical wall by vapor
deposition. In examples of the present disclosure, the upper fixed
sensing combteeth set of the sensing comb assembly 1322 is
electrically connected to the upper pad 1392 and the lower fixed
sensing combteeth set of the sensing comb assembly 1322 is
electrically connected to the lower pad 1394.
[0042] Those of ordinary skill in the art may recognize that
modifications of the embodiments disclosed herein are possible. For
example, the number of vertically actuating comb assemblies may
vary; the number of springs may vary; and the shape and the size of
the mirror may vary. Other modifications may occur to those of
ordinary skill in this art, and all such modifications are deemed
to fall within the purview of the present invention, as defined by
the claims.
* * * * *